Contact drum and method for heat exchange with traveling strip



Dec. 3, 1968 CONTACT DRUM AND METHOD FOR HEAT EXCHANGE WITH TRAVELING STRIP Filed D60. 26, 1967 W. RALL s m. I Fla-1 a: IH 11% 11-: IWI mm, 7 32 33 32 3 I6 /5 l7 l8 /4 g 2 j 10.. 22 W 27 j 2 W W /92: 2o 1 i 19 I6 I valor wafer g ,3

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United States Patent ABSTRACT OF THE DISCLOSURE A contact cooling drum for strip being processed in a vacuum has a connection supplying gas at low pressure to the interior thereof and normally closed valves in its surface opened by engagement of the strip, therewith. A limited amount of gas thus flows into the space between the drum surface and the strip bent around it, which greatly increases the rate of heat transfer from the strip to the drum surface.

This is a continuation-in-part of my application Ser. No. 513,328, filed Dec. 13, 1965, now abandoned.

Background of the invention This invention relates to a method and apparatus for exchanging heat with traveling strip in a vacuum and, in particular, to a drum for cooling metal strip passing around it.

In certain industrial processes, specifically the coating of strip by condensation of metallic vapor in a vacuum, it is important to prevent the strip from reaching too high a temperature, e.g., as a result of the heat gained thereby from the condensation. Cooling metal strip in a vacuum by passing it around cooled drums is relatively ineffective, however, because of the low rate of heat transfer. In actual practice, only about 1 percent of the apparent area of contact makes sufficiently good contact to provide a good rate of heat transfer. I have discovered that this rate may be materially increased by releasing a limited amount of gas into the space between the strip and drum. My invention concerns a method and apparatus for carrying out this procedure in a commercial operation.

Brief summary of the invention In accordance with my invention, I provide a cooling drum around which strip travels in a vacuum-processing chamber, with a connection to the interior thereof supplying gas at a low pressure. I also place valves in the drum surface having portions projecting outwardly thereof and thereby adapted to be engaged by the strip as it comes in contact with the drum, thus opening the valves successively as the drum rotates. Opening of the valves admits a small amount of gas leakage from the interior of the drum to the slight space between it and the strip. Such leakage afiords a convection medium increasing the rate of heat transfer from strip to drum without materially increasing the gas pressure in the processing chamber as a whole.

Brief description of the drawings A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawings illustrating the present preferred embodiment. In the drawmgs:

FIGURE 1 is an axial section through a contact drum embodying my invention, with parts in elevation;

FIGURE 2 is a transverse section taken along the plane of line II-II of FIGURE 1;

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FIGURE 3 is a fragmentary plan view showing a small portion of the drum periphery with parts broken away and in section for clarity; and

FIGURE 4 is a portion of FIGURE 2 to enlarged scale.

Detailed description of the preferred embodiment Referring now in detail to the drawings, the embodiment of my invention there shown comprises a drum indicated generally at 10 having a double-walled barrel or body 11 and double end walls 12 and 13. Body 11 may be roughened, knurled or otherwise surface textured to improve the distribution of gas admitted between it and the strip by means explained later. The drum is journaled in a vacuum chamber and is driven by a shaft 14 keyed to a hub 15 on end wall 12. End wall 13 is secured by screws 16 to the rotating member 17 of a special bearing 18 having passages for the inflow and outflow of fluid to and from the drum. This bearing is a commercially available product, the BT Rotorseal made by Fawick, Inc., Cleveland, Ohio. It has inlet and outlet pipe connections 19 and 20 for cooling water and an inlet connection 21 for gas.

Drum 10 has an axial tube 10a extending from a hub 22 on wall 13 to the inner plate of wall 12. Hub 22 has seals 23 to prevent leakage of fluid and receives the inner end of the center of member 17 which has a passage 24 therethrough communicating with pipe connection 19. Water is thus supplied through tube 10a to end wall 12 and flows radially to the space between the double walls of barrel 11. The inner plates of walls 12 and 13 are notched to provide communication between the interior of the end walls and the barrel space. A continuous flow of water may thus be maintained through the circumference of the drum. The outflowing water leaves through a cylindrical passage 25 in member 17 which communicates with a similar passage 26 in hub 22, and with connection 20.

Gas connection 21 communicates with a second cylindrical passage 27 in member 17. Gas tubes 28 in end wall 13 place passage 27 in communication with the interior of drum 10. As shown in FIGURE 2, tubes 28 are circumferentially spaced at a common radius about the axis of the drum. Connection 21 extends to any convenient source of any suitable gas, e.g., air or hydrogen under low pressure.

Elongated valve pockets 29 are spaced circumferentially about the interior of drum 10 and terminate outwardly in slots 30 in the periphery of the drum. Bars of T-section form valves 31, movable radially in pockets 29. The sides of the valves fitting in slots 3'0 are grooved as shown at 31a in FIGURE 3. An elongated closure member 32 of channel section, having holes 32a therein, is secured over each valve pocket 29 and springs 33 therein constantly urge the valves toward closed position.

A drum of the construction described is highly effective for cooling a traveling strip S trained around it in a vacuum chamber. As each valve engages the strip, the valve is displaced slightly and opens to admit gas from the interior of the drum to the space between drum and strip. Since the drum is in a vacuum chamber, a very low pressure of gas inside the drum will suflice to cause the desired outflow. After full engagement of the drum by the strip, the slots 30 are substantially blocked thereby but sufiicient gas flow occurs nevertheless into the space between strip and drum because of slight leakage.

The distribution of this gas throughout the region of contact of the drum by the strip may be made more uniform by suitably texturing the drum surface.

It is apparent from the foregoing, that, by the drum of my invention, I am able to introduce small amounts of gas between the strip and the drum as the former approaches contact with the latter and to continue supplying gas to the space between strip and drum as long as they are in contact. This greatly increases the efiiciency of heat transfer between the drum and strip.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention as set forth in the claims.

I claim:

1. A method of exchanging heat in a vacuum by contact between a drum and a strip traveling around it, the steps comprising maintaining gas under low pressure in said drum and admitting gas from the drum to the space between it and the portion of the strip in contact therewith while circulating cooling fiuid to and from the drum.

2. Apparatus for cooling strip during processing in a vacuum comprising a cylindrical drum journaled for rotation on its axis, said drum having a plurality of ports in its peripheral surface, a valve for each port having a portion normally projecting outwardly through the port and adapted to be engaged by the strip when in contact with the drum to open the valve, and means supplying a gaseous medium to the interior of the drum.

3. Apparatus as defined in claim 2, characterized by the peripheral surface of said drum being textured.

No references cited.

ROBERT A. OLEARY, Primary Examiner.

C. SUKALO, Assistant Examiner. 

